1. Field of the Invention
This invention relates generally to internal combustion engines and more particularly to linear internal combustion engines.
2. Description of the Related Art
The vast majority of internal combustion engines currently in use are reciprocating engines in which a piston moves up and down within a cylinder. The linear motion of the piston is translated into rotary motion by a crankshaft connected to the piston by a piston rod. In a typical engine, due to the large forces involved, the coupling between the crankshaft and the piston rod and between the piston and the piston rod, is a simple journal bearing. Accordingly, significant friction is introduced when converting the reciprocating motion of the piston to rotary motion.
Current internal combustion engines further require complicated valving mechanisms in order to introduce fuel and air into the cylinder and to release exhaust gases. Typically such mechanisms involve spring loaded valves that are biased toward the closed position. Cams, driven by the crankshaft open and close the valves at appropriate times by pushing against valve stems attached to the valves. The contact between the cam and the valve stems is typically a sliding contact introducing a great deal of friction just to open the valve.
Free piston engines reduce mechanical complexity and losses resulting from the conversion of reciprocating motion to rotary motion by extracting energy from the reciprocating movement of one or more pistons free to move within a cylinder. However, free pistons are difficult to control in order to execute a multiple-phase combustion process. Furthermore, currently available systems typically require complicated valving mechanisms similar to those in traditional internal combustion engines. Accordingly, such systems have been cumbersome and unfeasible at small scales.
Accordingly, it would be an advancement in the art to provide a linear engine capable of extracting energy from a combustion process without requiring conversion of linear motion into rotary motion. It would be a further advancement in the art to provide such a system that eliminates the need for complicating valving or control mechanisms. Such a system would be scalable for use in both high power and low power applications.